Curtainwall architecture comprises both vision areas and opaque areas referred to as spandrels. Spandrel areas are formed by panels which are either intrinsically opaque or made opaque by the inclusion of an opaque coating or backing material. Spandrel panels are generally employed to conceal portions of the structure of a building which are not aesthetically pleasing if visible from the exterior of the building. For example, spandrel panels may be used to conceal floor slabs, air conditioning equipment, heating ducts and so on. Spandrel panels may also be used to maintain privacy or security, e.g, at the ground level of a building.
A variety of spandrel panels that closely match or pleasingly contrast in color and reflectivity with adjacent transparent glass panels in curtainwall construction have been developed. Increasing use of highly reflective transparent metal and metal oxide coatings has led to the development of matching spandrel panels. U.S. Pat. No. 3,869,198 discloses spandrel panels provided with a transparent light and heat reflective coating on the outwardly glazed glass surface and a substantially opaque ceramic enamel coating adhered to the inwardly glazed glass surface. These spandrels provide for aesthetically matched vision and spandrel areas in curtainwall construction by utilizing a ceramic enamel coating which reflects light in the same spectral region as the light transmitted by the transparent coating and glass combination. U.S. Pat. No. 3,951,525 discloses spandrel panels with transparent light and heat reflective coatings on the inwardly glazed glass surface and with substantially opaque ceramic enamel coatings adhered to the transparent light and heat reflective coatings. The spandrels are aesthetically matched to vision areas in curtainwall construction by utilizing a ceramic enamel coating which reflects light in the same spectral region as light transmitted by the transparent coating.
In some architectural installations, it is desirable to have a spandrel panel which has a different surface appearance from the high reflectivity of a metal or metal oxide coating or the glossiness of glass. U.S. Pat. No. 4,394,064 to Dauson discloses a durable spandrel panel comprising a rigid panel substrate, a ceramic enamel coating of a desired color, and a transparent protective metal oxide overcoating. In some applications, the substrate is preferably transparent, so that the color of the ceramic enamel coating is visible from both the exterior and the interior of the building. Glass is a particularly desirable substrate.